<p>Happiness and sustainability represent two fundamental yet distinct priorities - individual well-being and planetary welfare - both central to contemporary policy agendas. As the world faces growing environmental and social challenges, understanding the nature of the relationship between these two dimensions is critical for designing effective and integrated public policies. While previous studies have reported a positive association based on correlations or ordinary least squares regressions, such methods are limited by assumptions of normality and are sensitive to multicollinearity. In this study, we adopt a more robust methodological framework using regularized regression and copula-based models to analyze data from 126 countries in 2022. We first assess the direct dependence between happiness and sustainability using copula-based models and regularized regressions. The results confirm the presence of co-movement between the two variables, but do not reveal the underlying factors driving this dependence. Then, after employing regularized regressions to filter out the effects of shared factors, namely institutional qualities, per capita income, and life expectancy, our copula-based analysis reveals no remaining significant residual dependence between happiness and sustainability. The best-fitting copula model (Frank) indicates weak and statistically insignificant dependence, indicating that the observed relationship is primarily attributable to the influence of common explanatory variables. These findings call for a more nuanced interpretation of the happiness–sustainability nexus and underscore the importance of targeting institutional and socioeconomic drivers in policy design.</p>